1. Field of the Invention
The present invention relates to an instruction supplier, and more particularly, to an instruction supplier which is capable of preventing a functional error from taking place based upon an instruction sequence of a microprocessor.
2. Description of the Related Art
Since a microprocessor perform very logically complicated operations, there occurs various functional erroneous operations in the development stages thereof. Furthermore, it has become difficult to conduct a functional simulation including all instruction sequences within a predetermined practical time which may take place during its design stages. Therefore, in a design, a functional verification and a trial manufacture of each microprocessor, a confirmation of functional operations is performed by executing various test programs therein.
For this purpose, with respect to the erroneous functional operations taking place at an evaluation stage, the logic circuit and mask layout of the microprocessor is to be modified, which tends to extend the development time thereof. Particularly, with respect to a functional error operation taking place only in a complicated instruction sequence (for example, a case where a specific instruction is executed immediately after a floating decimal point calculation instruction), since the functional error can be found only in a program containing such an instruction sequence, it takes an extremely long time to confirm the functional operations of the processor.
In some cases, functional errors may be found after placing the microprocessor on the commercial market (for example, the i486 type microprocessor manufactured by the Intel Corporation, in the fall of 1989).
As described above, it is very difficult and it takes a long time to insure that a microprocessor can perfectly operate for all programs. Conventionally, when such a functional error operation takes place, a determination is made as to whether or not a modification of the software may cope therewith. If it is possible, the software is modified in many cases.
As described hereinabove, in the case where a functional error takes place, the general trend is to prevent the functional error by changing the compiler or the object code thereof. However, such a change in the software may involve a functional erroneous operation of the software. Furthermore, in the case where the software can not prevent the erroneous operation, there arises such a problem in that it take a longer time to develop and complete a microprocessor design because it is necessary to modify the logic circuit and the mask layout of the microprocessor.